« EdellinenJatka »
is being given to the merchant marine this is not so great a disadvantage. Circumstances might arise, however, in which we might be called upon to dock a vessel of greater length.
The superintendent of the Leyland line of steamers instructed one of their captains to learn whether or not there were facilities for docking one of their ships in Boston should she meet with any mishap requiring her to go into dock.
into dock. After making inquiries at the different docks in Boston he called upon me in company with a friend to learn if our dock would take one of their ships, the shortest one of the company's steamers being three hundred ninety-two feet between perpendiculars. It is needless to say that it could not be docked. The sectional docks are unlimited in capacity, but the great requirement, rigidity, is not found. Although means are now employed to obviate this trouble to a very marked extent, still there is much danger to be apprehended from the strains which are liable to be thrown upon a ship, arising from emptying the different sections unequally, and the greater the number of sections the greater the danger to be apprehended.
The balance dock is, next to the dry dock, the least open to the objections offered to the sectional dock, but still it is a cumbersome affair and, like all lifting docks, the cost of maintenance is great. The addition of railways upon which to haul the ship from any one of the floating docks I think injurious. It is almost an impossibility to place a road on a bed sufficiently rigid and level to haul a vessel upon without doing more or less damage to her, although this is the plan proposed by no less eminent an engineer than Captain Eads for transferring ships across the isthmus of Panama. I do not propose to set myself up in opposition to Captain Eads, but were I the owner of a good ship I would want to see how his plan worked with some other person's vessels before I risked mine ; with small vessels there is no reason why they should not be lifted and run upon a railway for storage or repairs, but for large vessels I must say, that I do think there is danger of racking and twisting them.
There is a system of dockage now in use at Nicolaieff in the Russian dock yard, which, in my opinion, is the best yet devised. It possesses the advantage that at almost a nominal cost it can be extended as far as the requirements of the service may dictate. This system consists of a lifting dock of peculiar mechanism and a series of piling, arranged in clusters, upon which the vessel is deposited. The dock is a large rectangular box thoroughly trussed and braced, to which is rigidly attached a number of pontoons also completely trussed; the entire structure being built so as to make it as rigid as possible. On the side of the rectangular box opposite the pontoons is placed a counterpoise very ingeniously designed. The pontoons are so arranged that the dock can be hauled in against the piling, the pontoons passing in between the clusters of piles. In docking a vessel, a cradle very strongly braced to add to the rigidity of the structure is placed upon the dock, and the whole is sunk; the ship is then hauled over the dock and placed in the proper position, the pumps are started, the pontoons emptied and the vessel lifted, the dock is hauled into the piling, the pontoons slowly filled, causing the dock to sink leaving the vessel in its cradle resting on the piles, and in position for any repairs or work to be done. When a ship is ready to be put afloat the dock is sunk, and hauled in under her, the pontoons emptied, the vessel lifted from the piles, and her cradle hauled out, the dock sunk, leaving the vessel afloat. When a vessel is built she is started and completed in a cradle, and, when she is ready to put afloat the dock is called into use, and she is floated as above described, thus avoiding all danger of straining her in launching,-should it become necessary to dock a vessel when all the space is occupied, all that is required to accommodate her is to drive more piles, brace and cap them, and they are ready for use.
Mr. Clarke, the engineer who built the dock, took every precaution to make the risk to a vessel, while being lifted, a minimum. In testing this dock a vessel was lifted and floated twice in a violent gale of wind, and the action was in every way highly satisfactory. By this dock and its piling the Russian Government obtained, for an expenditure of £200,000 sterling, facilities equal to twenty ordinary stone docks, each one of which would have cost at least, $ 1,000,000.
For the purpose of laying up vessels not required for service this system is very superior, both the time necessary to lift and deposit a vessel and also that consumed in floating her again being very small, while space on the water-front, not otherwise required, can be prepared and used for this purpose.
I will now lay before the institute an idea for which I claim originality, not in the means used but in the application thereof. A dam of peculiar construction has been in use for some years, in France, in streams which at periods require facilities for slack water navigation. Our government is about finishing one in the Ohio river at Pittsburg. The peculiar feature of this dam is that when there is a good boating stage of water, and there is no need of the locks for the passage of vessels it lies flat on the bottom of the river; but when the water becomes so low that navigation is impeded the dam is raised up in short sections, and the water held back, and vessels pass through the locks, I think only two men are required to set the dam up, a section at a time; when there is a rise in the river the top of the dam buoys up, the props are pulled out from the sockets in the apron, and the whole structure is laid upon the bottom. This action is automatic.
While studying this dam and its working I conceived the idea of applying it to ship-yards for dockage purposes.
I have considered the plan in connection with a wet basin estimated for, located in the site now occupied as a timber basin, between the steam engineering machine shop and the construction buildings near the dry dock. The plan, as recommended to the Secretary of the Navy, contemplated the excavation of the site to a proper depth, I think thirty-one feet, with a lock, which, being connected with the pumps of the dry dock, could be used as a dock for such work as cleaning bottoms and making slight repairs.
To carry out my ideas I would pile a portion of this basin, if not the whole, and put in a heavy concrete floor; attached to this floor will be structures built on the principle of the dam, enclosing spaces suitable for landing vessels on the floor; there will be also cross dams allowing the use of a longer or shorter portion as needed. Ordinarily these dams will lie upon the bottom of the basin out of the way of any vessels to be moved from one part of the basin to another,
When it is necessary to expose the bottom of a vessel the following course will be pursued. She will be put in a cradle and taken to that part of the basin where she is to be landed, the sections of the dam enclosing the space will be raised and secured in place, the pumps will then be started ; before the level of the water within the enclosure shall have been lowered sufficiently below that without to throw an under strain upon the structure the vessel will have been landed, and the introduction of shores will have commenced; and by the time the enclosure is pumped out the shoring will have been completed, and the vessel will then rest in perfect safety. I have not worked up the details of construction of the sides I would use. The material should be wood with copper fastenings, and the walls being double, so connected that when lying on the bottom they would come together, but when lifted into place they would be four or five feet apart, with internal toggled bracing which would come into play as bracing when, in raising the walls, they had almost reached the point at which they are to remain. Were I going to construct this work in a locality where the teredo abounds I should use iron, unless the experiments now being conducted by the Corps of Engineers of the Army show that the teredo does not attack wood which has been treated by the Thilmany process. In that case I would prefer the wood, as more lasting. I propose soon to prepare detailed drawings of a work of this nature, and then I will be able to give an estimate of the cost. The estimated cost of the wet basin heretofore submitted for consideration is one million four hundred thousand dollars. I think with an additional expenditure of about one million dollars facilities for docking six vessels in the basin could be provided. Were a vessel docked as set forth there would be no more risk attending the operation than in putting her in a stone dock. The water in the basin being kept at a constant level, through the interposition of the lock, floating platforms and cranes could be used in carrying on the work. Before floating a vessel it would be necessary to thoroughly clean the floor and remove therefrom all chips and pieces which might in any way interfere with the raising or lowering the sections of the walls; for the same reason it would be necessary to allow no surface drainage to go into the basin with material to be deposited therein. With proper care I believe that such plan would, if carried out, prove highly satisfactory, both as to its action and cost of maintenance; and I would have no hesitation in recommending its adoption. As it would be an experiment I would suggest that it be tried with a single compartment at first, and then, if a success, additional compartments could be provided.
Leaving out of the question the class of docks to be constructed, there is no manner of doubt that a large increase of dockage is necessary. The idea of a naval ship-yard with facilities for docking but one vessel is ridiculous, and the very great inconvenience to which this condition of affairs would subject us in time of war is patent to all. Eyery yard in the service should be able to provide dockage for ten vessels; any variation from that number should be to increase rather than diminish it. There is no other element of dock-yard organization that possesses the importance of this one. Should a necessity arise throwing upon this yard double the amount of work it is now capable of doing everything could be provided and put in operation in thirty days, by simply preparing the beds for the tools, putting them in place, and throwing over them a temporary covering ; but instead of being called upon to do any such thing we are prevented from working the yard to its full capacity by the want of docks in which to repair vessels.
In the plan laid down for the development of this yard, and from which there was to be no deviation, five stone docks were provided for. Why they were not built no one can tell, but the omission of four of the five was a very serious mistake on the part of the authorities having control at that time.
It is a trite saying—"in time of peace prepare for war"; and now that Congress is waking up to the condition of the service, and taking initiatory steps looking to the building up of a navy creditable to us as a nation, I think that one of the most important things requiring consideration is to put our yards in condition to maintain the navy in good order for war purposes. We are well provided with shops, machinery et cetera, and what we need is a large increase of dockage, so that we can work the yards to good and full effect.
Comd'r SICARD. I have been very much struck with the economy of the Russian dock, which seems in every way admirable, and especially in point of expense; the only serious cost would be that of preparing one caisson or floating platform. The part attached permanently to the shore should not be very expensive, and is capable of indefinite expansion. The dock to be made by raising and lowering gates (such as is used for dams on the Ohio river) seems sufficiently easy to arrange and could probably be made tight without difficulty.
Hon. R. B. FORBES. I have long entertained the idea that every naval station on the sea coast should have a place for the storage of iron-clads; almost every naral station has rivers emptying near it and it would be perfectly feasible, in my opinion, to utilize fresh water now running to waste in supplying basins, docks or locks or storing iron-clads. I am not ready nor am I competent to say exactly how this should be done; I leave that to engineers. Let me say however that as the sources from which the streams come are niuch higher than the proposed basins or docks, I can conceive of no mechanical difficulty to prevent carrying out the idea. It would be altogether a question of money, and it will naturally occur to every one that the cost of the docks, and of the supply of water, may be too great to warrant carrying it out.
Perhaps the simplest plan would be to construct a basin for the storage either dry or afloat of three large ships. In time of peace, when movements would be rare, the expense of maintenance would be small, and in action, even if large, the expense would be a secondary matter. I shall not take up your time further than to say that competent engineers may do well to make estinates of the cost and maintenance of the docks. They need not be of fine hammered granite, nor need they be monuments of architectural skill like the dock near by; with strong sea walls and gates they may, I fancy, be built very cheaply, the land being the chief cost.
Civil Eng. WHITE. I would say in reply to Mr. Forbes's remarks on the subject of fresh water basins in which to lay up iron clad vessels that since I have been in the service I have been on two boards of engineers to lay out and prepare estimates for such works, one at Norfolk and the other at the New London station. The one at Norfolk covered twenty seven acres, the estimated cost being about one half million of dollars, including a lock five hundred feet long by eighty feet wide, and bringing water from the Dismal Swamp. The one at New London covered a space of seventeen acres, at an estimated cost of about four hundred thousand dollars. As a means for preserving iron clad vessels from the action of salt water, when not in service, I consider the Nicalaeiff system as the best plan now before the world.
Lieut. BASSETT. Mr. Chairman. I move that the thanks of this Branoh of the Naval Institute be tendered to Mr. White for his instructive paper.
The motion of Lieut. BASSETT was adopted.